Azurite Hue vs Deep Sky Blue

How close are they?

ΔE 20.2, loose: different enough that you should pick on purpose. Deep Sky Blue is noticeably lighter, cooler than Azurite Hue.

Can I use Deep Sky Blue instead of Azurite Hue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Deep Sky Blue is noticeably lighter, cooler than Azurite Hue.

Can I use Azurite Hue instead of Deep Sky Blue?

The same difference applies the other way round: Azurite Hue is noticeably darker, warmer.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.